The year is 1991. A plague has destroyed the dog and cat population of Earth and apes have replaced them as pets. But now apes have become slaves to their human masters, and one intelligent talking chimpanzee, Caesar (Roddy MacDowall), is determined to set the apes free...

The fourth episode in producer Arthur P. Jacobs' Planet of the Apes series was written by Paul Dehn. In many ways, and in spite of its predictability, it's the best of the sequels as it returns to the political themes that gave the original its depth and resonance. The difference here is that the apes are the oppressed victims, and the humans are the bad guys.

There is a definite sense of class war, and more pertinently, race war in Conquest. The apes are seen to be taking menial jobs like cleaning up, shining shoes and being waiters, all in the service of mankind. They are second class citizens, and the film deliberately draws parallels with slavery, which, while not exactly flattering, makes for an edgier drama.

McDowall comes across as a chimp Spartacus rallying his troops into revolt, which takes the form of a massive brawl filling up the whole of the last half hour of the movie, with apes and humans slaughtering each other. The future we see (well, it was the future in 1972) is a concrete and glass police state controlled by jackbooted cops led by the fascistic Governor (Don Murray). There are a few concessions to sci-fi technology, such as a torture device/lie detector, and green cigarettes that don't give you cancer.

Not all the humans are villains, Ricardo Montalban (from the previous film) plays Caesar's best friend, but doesn't last long, and one of the officials (Hari Rhodes) helps out Caesar when he sees the injustice of the apes' situation. But the final speech, where Caesar calls for death to all humans was noticeably softened by a "Well, let's be nice to them, really" addendum which looks out of place after all we've seen.

Still, considering Conquest is basically a third cash-in sequel, it's surprising it goes as far as it does with its civil rights message and pretentions to social commentary, and is none the worse for that. I know continuity isn't exactly this series' strong point, but how did the apes evolve so fast? Pseudo-Jerry Goldsmith music by Tom Scott.